Hi-
Your story sounds similar to mine, except that EI started with ST for feeding, and she (and her supervisor) knew nothing about sensory feeding issues, and we had to fight to get OT. Get recommendations for a good OT. EI doesn't always screen the therapists for experience and knowledge in your child's particular issues. We requested a new ST from our service coordinator, after realizing she had no clue how to help our son, and had been told by the evaluating ST he'd only need 6 months of therapy, and 3 months later, he'd made no progress (of course, the therapist went to China for a month right in the middle...)
You should have an OT, not an assistant. Even many OTs are not certified/knowledgeable about sensory issues. Call around. Many places will take Early Intervention clients. We found our own OT after waiting several months with no hope of getting one. But she did take Early Intervention, so it worked out. I learned that you can't rely on EI, but it's nice to have them pay.
Where are you located? We are in the northwest suburbs, and if you're near by, may have some recommendations for you. We've been through all this, including the school system as well. My son is about to turn 6, and eats better than his older sister. We did hit therapy hard when he turned 3, however; Besides the 2x a week school district OT and ST, we did private ST, a feeding therapist (who was an expert & understood about sensory on top of it!) and private OT 3 times every 2 weeks. Luckily, insurance covered everything but the feeding therapist.
I guess my advice is don't get rid of EI, but realize their limitations; they have a lot of clients waiting for services and any single child is not their priority. Definitely advocate for your child; Do some research and call around, ask for recommendations from other parents as well. Let me know where you are located; I belong to a local online group that may have some therapist recommendations for you! Good luck!
M.